Carburetor



pt 2, 1952 H. T. sco'r-r 2,609,187

CARBURETOR Filed Oct. 24, 1947 I 2 SHEETS--SHEET 1 V fi/ an INVENTOR.

HARRY 7T 5C0 TT )1 /2 BY T- -//l 3. 0k n E 2 15 ATTORNEY Sept. 2, 1952SCOTT 2,609,187

CARBURETOR Filed 'Oct. 24,1947 2 SHEETS-SHEET 2 38 3 v 40 70 5 36 mug MATTORNEY Patented Sept. 2, 1952 UNITED STATES m'rsnr OFFICE CARBURETOBHarry T. Scott, Los Angeles, Calif. Application October 24, 194.7,:SerialNo. 781,784 4 Claims. (01. 261- 23) My invention relatesgenerally to internal combustion engines, and more particularly tocarburetors for the fuel supply systems thereof.

Itisa fact Well known to those skilled in the art, that it is impossibleto design a single or dual carbureor which will deliver to the engine aneconomical, homogeneous combustible mixture without sacrificing power,or to design such carburetors to obtain maximum engine power andyetmaintain economical, smooth operation of the engine at the lowerspeeds. In designing a. carburetor for economy, the Venturi area must besufiiciently reduced to insure high velocity air for atomization of thefuel at the nozzle into the finest possible mist for mixing with air inthe mixing chamber into a homogeneous mixture. However, with awide openthrottle to'ob tain the maximum power-and speed of which the engine iscapable, the restricted venturi will limit the air entering the engineand will thus cause a back pressure or vacuum to be built up in theintake manifold. The volumetric efliciency of the engine is thusreduced, to the end that the engine cannot produce all'the power that itis capable of delivering.

n the other hand, if the Venturi area is increased sufficiently toobtain increased volumetric efliciency at the higher speeds, then thevelocity of air passing through the'venturi at the lower engine speedswill be insufficient to atomize the fuel.

The primary object of my invention is to provide a carburetorstructurally characterizedby simple, positively acting means whichovercomes the objections and defects of single and. dual typecarburetors as above set forth, and insures that aneconomicaL'homogeneous, combustible mixture will be delivered to theengine at all speeds without sacrificing any power that the engine iscapable of delivering.

Another object of my invention is to provide a carburetor of the abovedescribed character embodying one carbureting unit with a manuallyactuated throttle for the lower speeds, and a second carbureting unitwhose throttle for the higher speeds is operatively associated with thelow speed throttle in such manner that the high speed throttle will bemaintained closed until the low speed throttle reaches .a predeterminedopen position, preferably that at which maximum volumetric efficiency isderived from the mixing chamber of the one carbureting unit, andirrespective cf the vacuum present in the induction system of the engineat the downstream side of the throttles, the high speed throttle beingthen free to open in accordance. with the demand of the engine for fuel,whereby to economically obtain maximum volumetric efficiency from thecarburetor at all engine speeds.

With these and other objects in view, my invention resides in thecombinations, arrangements and functional relationships of elements asset forth in the following specification and particularly pointed out inthe appended claims.

In the'accompanying drawings,

Figure 1 is a view showing in vertical, longitudinal axial section, oneform of carburetor embodying my invention;

Figure 2 is a fragmentary view of the carburetor in side elevation, andshowing both low and high speed throttle valves closed;

Figure 3 is a horizontal sectional, view taken on the line 3--3 ofFigure 2;

Figure 4. is a vertical sectional view taken on the line 4-4 of Figure3, with the low speed throttle valve partly open and the high speedthrottle valve closed;

Figure 5 is a view'similar to Figure 4, but showing the low speedthrottle valve fully open, and the high speed throttle valve free toopen;

Figure 6 is a view similar to Figure 4, but showing the low speedthrottle valve fully open and the high speed throttle valve partly open;

Figure 7 is a fragmentary detail view partly in elevation and partly insection, of a spring adjusting means embodied in my invention; and

Figure 8 is a diagrammatic plan view showing the relation between thecarburetor and intake manifold of the engine to deliver fuel to thecommon induction system thereof from a concentrated area at thedownstream side of the low and high speed throttle valves.-

Referring specifically to the drawings, the carburetor embodying myinvention is shown for the purpose of illustration as being of thedowndraft type, and is composed of two carbureting units A and Bsupplying fuel to ,a common induction system of which the intakemanifold Iis shown .in Figure 8.

The single body H] which contains the carbureting units A and B is madeup of several sections bolted together as isthe common practice tofacilitate manufacture, and is provided in its lower portion with twoparallel bores II and I2, the upper portions of which are provided withVenturi members [3 and M, respectively. In the present instance thebores H and [2 are of the same diameter, but the member [3 has a throatof smaller area than the throat of the member M. It is to be noted thatthe efiective area of the venturi I3 is considerably smaller than theeffective area of the venturi embodied in the usual single Venturi typecarburetor for an engine of corresponding size.

In the bores II and I2 are throttle valves I5 and I6, the valve I5 beinghereinafter referred to as the main or low speed throttle valve for usein attaining road speeds of up to fifty or sixty miles per hour, whereasthe valve I6 will be hereinafter referred to as the auxiliary or highspeed throttle valve for use in addition to the throttle valve I5 inattaining road speeds above those possible with the throttle valve l5alone. As shown in Figure 1, the carbureting units A and B are providedwith main fuel nozzles 20 and 2| associated with the respective venturisl3 and I4, and idling fuel nozzles 22 and 23 associated with therespective throttle valves I5 and I6, all being supplied with fuel froma common float chamber indicated diagrammatically by 24 in Figure 8.

The throttle valve I5 is fixed to a shaft 25 journaled in the body Iabout an axis diametrically related to the bore Fixed to one projectingend of the shaft 25 is an actuating member in the form of an arm 26 towhich pivotally connected at 2! a throttle rod 28 which is controlled bythe usual foot throttle (not shown) spring loaded to urge the throttlevalve I closed in the usual manner. A lateral extension 29 on the arm 26has threaded therethrough an adjustable stop screw 30 which coacts witha stop lug 3| on the body ID to provide for idling adjustment of thethrottle valve I5. The arm 26 is further provided with a cam shoulder32, which, in the partially open position of the throttle valve shown inFigure 4, engages the beveled end 33 of a yieldable detent pin 34passing freely through an opening in a lug 35 on the body I 0 andmounted on the free end portion of a flat spring 36 whose other end iSIfixed to the underside of the stop lug 3| by a screw 31. The pin 34offers slightly noticeable resistance to the opening movement of thethrottle valve I 5 beyond the position of Figure 4, but yields tocontinued pressure on the foot throttle to enable the valve I5 to bemoved to the fully open position shown in Figure 5, to which positionthe valve is definitely limited by a stop shoulder 38 on the arm 26engaging the lug 35 as shown in this figure. The arm 26 is provided witha peripherally arcuate surface 39 which freely wipes across the end ofthe axially displaced pin '34 between these two positions of thethrottle valve I5.

The throttle valve I6 is fixed in an off-center position to a shaft 40journaled at one end in the body l0 and at the other end is a bushingor-sleeve 4| mounted in the body and projecting therefrom'as shown inFigure 3. A relatively lightly loaded coil spring 42 surrounds said oneend of the shaft 40 within a cup-shaped cap 43. One end of this springis fixed at 44 to the body I0, and its other end is fixed at 45 to thecap, which latter is rotatably adjustable on the shaft 40 to vary theloading of the spring. The cap 43 and shaft 40 are provided withcircular series of teeth 46 and 41, respectively (Figure 7) which lockthe cap in any selected position of adjustment.

A headed screw 48 threaded into the end of the shaft 4!] and bearingagainst the cap, confines the latter against axial displacement, withthe teeth 46 and 41 in mesh. When the screw 48 is loosened, the cap 4|can be shifted axially to disengage the teeth 46 and 41, so as to enablerotatable adjustment of the cap to be effected.

Fixed to the other end of the shaft 46 which projects beyond the bushing4|, is an anti-flutter or inertia member in the form of a weighted wheel50, from the inner side of which laterally projects an ear 5|. 5| is anadjustable stop screw 52 which co-acts with a stop lug 53 on the body I6, to provide for idling adjustment of the throttle valve I6, it beingclear that the spring 42 urges the stop screw 52 against the stop lug53.

Freely mounted on the bushing 4| is the hub 60 of a control member 6|. Arelatively heavily loaded spring 62 is mounted on the bushing 4| withinan enlarged portion 63 of the bore of the hub 60, with one end of thespring fixed to the body at 64, and the other end of the spring fixed tomember 6| at 65, all to the end that the spring will urge the controlmember to rotate in the same direction (counterclockwise in Figures 3 to6, inclusive) as the throttle valve I6 is urged by the spring 42, to theposition shown in Figures 2 and 4 wherein a lug 66 on the control memberengages the ear 5| of the inertia wheel 50.

A split, spring ring 61 co-acts with a washer 68 to confine the controlmember 6| against axial displacement, and a second washer 69 is mountedon the shaft 40 between the inertia member 50 and the end of the bushing4|, to reduce the friction against the inertia member to a negligibleamount.

The actuating member 26 is provided with a number of teeth providing asegmental gear 16 which is adapted to mesh with a segmental gear 1|formed by a number of teeth on the control member 6|, it being notedthat the second tooth at one end of the gear H is omitted to enable thegear II to move into and out of mesh with the gear 10, all in a mannerto be described in the operation of the invention which is as follows:

When driving in the lower speed range, which, in modern automobiles maybe considered as a maximum of from fifty to sixty miles per hour, onlythe carbureting unit A functions, the throttle valve I5 being manuallyopened from its idling position of Figure 2 to supply the necessaryfuel, by depressing the foot throttle in the usual manner. However, uponreaching the partially opened position shown in Figure 4, the throttlevalve I5 has been movedthrough an angular distance of approximatelysixty degrees, which represents the maximum throttle opening at whichvolumetric efficiency can be obtained. Any further opening of thethrottle valve I5 will not appreciably increase the power, due to therestricting effect of the Venturi member I3, which, it will beremembered, has designed for economy within the lower speed range.

The operator will be aware that the maximum open position of thethrottle valve |5 for maximum volumetric efiiciency has been reached, bycontact of the cam shoulder 32 with the beveled end 33 of the pin 34 asshown in Figure 4, as the pin offers a slight resistance to furtheropening of the throttle valve, which is felt at the foot throttle.Concurrently, the leading tooth of the gear '10 on the actuating member26 engages the leading tooth of the gear II on the control member 6|.Thus, should increased speed be desired, depressing movement of the footthrottle is continued so as to cam the pin 34 clear of the path ofmovement of the actuating Threaded through the ean' member whose arcuatesurface 33 wipes freely across the end of the pin.

As this movement of the control member 6| moves its lug 66 away from theear 5! of the inertia wheel 50, the high speed throttle valve I6 is nowfree to open against the slight loading of the spring 42 tending to keepthe valve closed. As a slight back pressure or vacuum is being built upin the common induction system at the downstream side of the carburetingunits, the valve !6 will be opened accordingly by suction thereon due tothe off center mounting of the valve on the shaft 49.

The additional mixture admitted to the engine, with the attendingincrease in engine speed, will naturally increase the vacuum at thedownstream side of the throttle valve 16, so as to further open sameuntil the ear 5| of the inertia Wheel 50 arrests the opening movement ofthe valve l6 by striking the lug 66 of the control member 6 I. Shouldopening movement of the low speed throttle valve be continued throughits maximum angular distance of approximately ninety degrees as shown inFigure 5, then the high speed throttle valve 16 may be opened until thespeed of the engine will not produce any additional slight vacuum in theinduction system. Under these conditions, the engine will be deliveringthe maximum power of which it is capable. It will be clear from theforegoing description, that an economical, homogeneous, combustiblemixture will be delivered to the engine throughout both low and highspeed ranges without sacrificing any power that the engine is capable ofdelivering.

I claim:

1. In an internal combustion engine, a carburetor comprising: aplurality of carbureting units having main and auxiliary throttlevalves, respectively; a rotatably mounted shaft to which said main valveis fixed; a second shaft to which said auxiliary valve is fixed offcenter, mounted for rotation about an axis laterally offset from andparallel to the axis of the first said shaft; means urging the secondsaid shaft to rotate in a direction to close the auxiliary valve; amanually operable actuating member fixed to the first said shaft; abushing through which the second said shaft projects; a control memberfreely mounted on said bushing; means urging the control mem ber torotate in a direction corresponding to that in which the second saidshaft is urged and with sufficient force to prevent manifold vacuum fromopening the auxiliary valve when the main valve is closed; an inertiamember fixed to the second said shaft; said control and inertia membershaving lugs co-acting under the action of said control member urgingmeans, to maintain the auxiliary throttle valve against openingmovement; and a lost-motion operative connection between said actuatingand control members, by which the latter will be rotated against itsurging means by the actuating member, so as to move the control memberlug away from the inertia member lug, to permit opening movement of theauxiliary valve to be effected by back pressure at the downstream sideof the valves.

2. A carburetor as embodied in claim 1 wherein said actuating member isprovided with a cam shoulder; and a yieldably mounted detent with whichsaid shoulder co-acts when the main valve has been opened apredetermined amount, to offer resistance to further opening of the mainvalve.

3. In an internal combustion engine, a carburetor comprising: aplurality of carbureting units having a main throttle valve and anunbalanced auxiliary throttle valve, respectively, and shafts to whichthe respective valves are fixed, to mount them for rotationindependently about laterally ofiset and parallel axes; a manuallyoperable actuating member fixed to the shaft of the main valve; acontrol member freely mounted on the shaft of the auxiliary valve; meansurging said control member to rotate in a direction to close theauxiliary valve; an inertia member fixed to the shaft of the auxiliaryvalve; said control and inertia members having stop co-acting under theaction of said urging means, to maintain the auxiliary valve closed; anda lost-motion operative connection between the actuating and controlmembers including gears by which the control member will be rotatedcounter to its urged direction when said main valve has been opened to apredetermined position, so as to move the control member away from theinertia member stop to free the auxiliary valve for opening movement byvacuum in the induction system at the downstream side of the valve; theratio between said gears being such that opening movement of the mainvalve beyond said predetermined position to a maximum open position willrender the auxiliary valve free to move from its closed position to amaximum open position so as to obtain maximum volumetric efficiency fromboth carbureting units.

4. A carburetor as embodied in claim 3 wherein at least one tooth of oneof said gears is omitted to facilitate meshing of said gears when theauxiliary valve is to be freed for Opening movement as aforestated,whereby to compensate for variations in idling adjustment of theauxiliary valve.

HARRY T. SCOTT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,152,031 Lobdell Aug. 31, 19151,916,906 Aseltine July 4, 1933 2,140,776 Trisler Dec. 20, 19382,193,533 Kishline et al Mar. 12, 1940 2,307,486 Carlson Jan. 5, 19432,402,361 Bicknell June 18, 1946 2,420,925 Wirth May 20, 1947 2,436,319Meyer Feb. 17, 1948 2,443,464 Leibing et a1 June 15, 1948

